As a method of forming a high-quality semiconductor film, there is known an epitaxial growth technique of growing a single-crystal film on a substrate such as a wafer by the vapor phase growth. In a vapor phase growth apparatus that uses the epitaxial growth technique, a wafer is placed on a support portion inside a reaction chamber that is maintained in a normal pressure state or a reduced pressure state. Then, a process gas such as a source gas used as a raw material for forming a film is supplied from, for example, a shower plate (or a shower head) at the upper portion of the reaction chamber to a wafer surface while the wafer is heated. Thus, a thermal reaction of the source gas occurs on the surface of the wafer, and hence an epitaxial single-crystal film is formed on the surface of the wafer.
In recent years, a semiconductor device using GaN (gallium nitride) has been gaining attention as a material of a light emitting device or a power device. As the epitaxial growth technique that forms a GaN-based semiconductor, a metal organic chemical vapor deposition (MOCVD) is known. In the metal organic chemical vapor deposition, for example, organic metal such as trimethylgallium (TMG), trimethylindium (TMI), and trimethylaluminum (TMA) or ammonia (NH3) is used as the source gas.
In the MOCVD, in order to form a uniform film on the wafer surface, the amount of the organic metal in the source gas needs to be stabilized. JP-A 2002-313731 discloses a configuration in which the pressure inside a source gas supply path is maintained in a constant range and a uniform film is formed on a wafer surface.